## Search found 49 matches

Sun Mar 18, 2018 1:45 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cp & Cv?
Replies: 3
Views: 432

### Re: Cp & Cv?

The above answers, are correct, pressure is able to change while volume stays constant
Sun Mar 18, 2018 1:33 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Value of “k” in Kinetics
Replies: 5
Views: 494

### Re: Value of “k” in Kinetics

if it is more than one, the forward rate is faster, and less than one the reverse rate is faster
Sun Mar 18, 2018 1:30 am
Forum: Phase Changes & Related Calculations
Topic: Energy from constant pressure versus constant volume RXN
Replies: 2
Views: 282

### Re: Energy from constant pressure versus constant volume RXN

Are you asking like if the changes in in pressure and volume or the same in their respective situations.
Sun Mar 11, 2018 9:51 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.37
Replies: 2
Views: 244

### Re: 14.37

Yeah I believe that should be fine, just make sure they are able to cancel like you did.
Sun Mar 11, 2018 9:49 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.65 (c)
Replies: 2
Views: 202

### Re: 15.65 (c)

The reasoning is better explained in section 15.11, but I believe it is due to the reaction having Arrhenius behavior, which allowed for the conclusion to be made about the k relating to activation energy.
Sun Mar 11, 2018 9:34 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Buffer Solutions
Replies: 2
Views: 228

### Re: Buffer Solutions

I did not see it on the things we should be able to do for the electrochemical section, so I doubt it.
Sun Mar 04, 2018 7:31 pm
Forum: First Order Reactions
Topic: Units in 15.29
Replies: 2
Views: 227

### Re: Units in 15.29

I think it is fine to leave the time units in terms of what the question gives you, unless they explicitly ask it for something else
Sun Mar 04, 2018 7:30 pm
Forum: Second Order Reactions
Topic: 15.39a
Replies: 2
Views: 224

### Re: 15.39a

The coefficient is not necessary in the second order formula and the question gives you the other needed values
Sun Mar 04, 2018 7:22 pm
Forum: General Rate Laws
Topic: Knowing rate law equations
Replies: 5
Views: 374

### Re: Knowing rate law equations

We probably won't be asked to show the derivations but just knowing them helps give a better understanding of the relationships which we will be asked about in the concept portion of the exam
Sun Feb 25, 2018 8:35 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: anode vs cathode in non standard cell diagram
Replies: 5
Views: 392

### Re: anode vs cathode in non standard cell diagram

Its usually set up for the anode on the left and cathode on the right, but its good to know that oxidation occurs at the anode and reduction occurs at the cathode if they try to flip it around
Sun Feb 25, 2018 8:27 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Initial Rates
Replies: 3
Views: 245

### Re: Initial Rates

I'm pretty sure it is fine to assume they are all initial rates, and if it isn't, it will probably be stated explicitly
Wed Feb 21, 2018 2:43 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Example 14.6 in Textbook, page 581 [ENDORSED]
Replies: 3
Views: 260

### Re: Example 14.6 in Textbook, page 581[ENDORSED]

You get them from the number electrons transferred in the respective half reactions. These are the n values from the equation given on page 572 in the textbook.
Tue Feb 13, 2018 12:09 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating K for partial pressures
Replies: 1
Views: 154

### Re: Calculating K for partial pressures

I doubt they would give the pressures to you one way and ask for them in another. However, on the off chance they do, you would have to convert them. But again, I don't think they want us focusing on knowing those conversions.
Tue Feb 13, 2018 12:06 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: K_b
Replies: 2
Views: 236

### Re: K_b

I believe you are referring to the Boltzmann constant, which is R divided by Avogardos number
Tue Feb 13, 2018 12:02 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Example 9.8
Replies: 2
Views: 185

### Re: Example 9.8

You know that there are 4 different orientations it could have which gives you the base 4. They call it 4^N because that is based on how many molecules you have. Im not sure where you are getting the ^4 from however.
Tue Feb 06, 2018 10:58 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.31
Replies: 2
Views: 202

### Re: 9.31

They say mass of polyethylene in the problem which I think may be the indication that it is a solid. That is just my guess, if that is just a coincidence, I am also confused on how we would know.
Tue Feb 06, 2018 10:53 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.19
Replies: 1
Views: 140

### Re: 11.19

They used calcite in the solutions manual but I agree that the difference would be negligible
Tue Feb 06, 2018 10:46 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: production vs consumption
Replies: 1
Views: 176

### Re: production vs consumption

I believe so
Sun Feb 04, 2018 10:36 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: pressure and free energy
Replies: 2
Views: 188

### Re: pressure and free energy

When they ask you to calculate the Gibbs free energy at certain partial pressures is when you use it. It just depends on what they give you in the question.
Sun Feb 04, 2018 10:30 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Entropy and Disorder
Replies: 1
Views: 137

### Re: Entropy and Disorder

I think its because he does not want to over simplify it. If he were to associate it with disorder, we might miss the more complex ideas associated with entropy.
Sun Feb 04, 2018 10:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Units for pressure in Gibbs Free Energy calculations
Replies: 1
Views: 130

### Re: Units for pressure in Gibbs Free Energy calculations

I think its in bars, but we have used atm in class interchangeably since the difference is almost negligible
Sun Jan 28, 2018 11:02 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: example 9.2
Replies: 2
Views: 174

### Re: example 9.2

Can someone elaborate on whether or not there is a pressure change, and if so how can you tell?
Sun Jan 28, 2018 10:51 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Universe being isolated
Replies: 3
Views: 279

### Re: Universe being isolated

the idea of the universe is an assumption, it is not proven. Hypothetically speaking, it is similar to a calorimeter because it wouldn't allow for mass and energy to be exchanged with it's surroundings.
Sun Jan 28, 2018 9:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: About entropy and gibbs free energy
Replies: 2
Views: 195

### Re: About entropy and gibbs free energy

It is because it is coupled with a spontaneous reaction
Sun Jan 21, 2018 7:36 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Intensive vs. Extensive Properties
Replies: 4
Views: 252

### Re: Intensive vs. Extensive Properties

Specific heat does not depend on the amount of substance, it only takes the mass into account in order to see how the temperature of the substance is affected. The definition of specific heat capacity is the amount of heat required to raise temp of 1 gram of a substance 1 degree celsius. I hope this...
Sun Jan 21, 2018 7:30 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity
Replies: 2
Views: 159

### Re: Heat capacity

I believe it has to do with the fact that different phases have different degrees of freedom
Sun Jan 21, 2018 7:23 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework Problem 8.99
Replies: 1
Views: 127

### Re: Homework Problem 8.99

After you find the enthalpy per mole of zinc consumed(-153.89 kJ/mol), you can multiply by the mols of zinc you started with(0.130 mol) to get the energy released by the reaction (about -20.0 kJ). Since they tell you molar heat capacity of the solution is the same as those of water you can plug in t...
Sun Jan 21, 2018 7:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity vs Specific Heat Capacity
Replies: 2
Views: 171

### Re: Heat Capacity vs Specific Heat Capacity

Dr. Lavelle mentioned in lecture that the heat required to raise the temp of an object by 1 degree Celsius is the heat capacity. This is an extensive property because the heat required depends on the amount of substance. The specify heat capacity is the heat required to raise 1 gram of a substance 1...
Sat Jan 13, 2018 6:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy of Formation from Most Stable Form
Replies: 3
Views: 638

### Re: Standard Enthalpy of Formation from Most Stable Form

When it is 0 it means the element began in its most stable from like the O2 example you described, the N2 example would not be 0
Sat Jan 13, 2018 5:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy vs. Bond Dissociation Enthalpy
Replies: 3
Views: 473

### Re: Bond Enthalpy vs. Bond Dissociation Enthalpy

I believe the two terms are interchangeable
Sat Jan 13, 2018 5:43 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: work equation
Replies: 2
Views: 168

### Re: work equation

As long as you know all the required variables it should always work, it just depends if the equation is necessary in the problem you are doing
Mon Dec 04, 2017 2:44 pm
Forum: Resonance Structures
Topic: Delocalization of Charge
Replies: 3
Views: 344

### Delocalization of Charge

There was a question on the test about the delocalized pi bonding.
Today in lecture, Dr. Lavelle was discussing delocalization of charges due to resonance.
Are these ideas like the same thing or are they different, if they are different could you explain the difference.
Mon Dec 04, 2017 2:37 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Equation derived from the conjugate seesaw
Replies: 2
Views: 215

### Equation derived from the conjugate seesaw

When Dr. Lavelle was demonstrating how to obtain a new equation be taking the -log of both sides from the Kw = Ka * Kb equation, the equation we got was
14 = -pKa + pKb
Why is the pKb postive, why wouldn't it be negative like pKa?
Sun Dec 03, 2017 11:40 pm
Forum: Octet Exceptions
Topic: Expanded Octet Rules
Replies: 7
Views: 645

### Re: Expanded Octet Rules

It begins with the non-metals in the third period or below, they are able to do this because they have empty d subshells that can house the extra electrons.
Sun Dec 03, 2017 11:36 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs. Lewis
Replies: 4
Views: 353

### Re: Bronsted vs. Lewis

A bronsted acid is a proton donor, while a Lewis acid is an electron acceptor
Sun Nov 26, 2017 11:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 4
Views: 339

### Re: Bond Angles

I don't believe it is required but it is pretty helpful to know them for each of the arrangements
Sun Nov 26, 2017 6:51 pm
Forum: Dipole Moments
Topic: Polarity based on number of lone pairs
Replies: 2
Views: 235

### Re: Polarity based on number of lone pairs

Lone pairs force the molecule to not be symmetric and thus polar
Sun Nov 19, 2017 11:13 pm
Forum: Hybridization
Topic: bond strength
Replies: 3
Views: 271

### Re: bond strength

Pi bonds are weaker because there orbital paths are parallel which results in the overlap between the p-orbitals to be less than those of sigma bonds.
Sun Nov 19, 2017 10:59 pm
Forum: Sigma & Pi Bonds
Topic: double bonds
Replies: 5
Views: 566

### Re: double bonds

Because when two atoms are bound by more than one covalent bond, then the additional orbitals overlap side by side to form pi bonds. And a double bond has one sigma bond and one pi bond.
Sun Nov 12, 2017 11:40 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity Exception
Replies: 3
Views: 1226

### Re: Electron Affinity Exception

Does this exception remain true for the rest of the elements in group 15?
Sun Nov 12, 2017 10:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone pairs versus bonding pairs
Replies: 3
Views: 481

### Lone pairs versus bonding pairs

What makes lone pair electrons have a different effect on the shape of the molecule versus if it was just another bonding pair?
Sun Nov 05, 2017 11:46 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge For Element In The Middle [ENDORSED]
Replies: 3
Views: 467

### Re: Formal Charge For Element In The Middle[ENDORSED]

Dr. Lavelle also mentioned that the formal charge and the molecule's overall charge should be equal.
Sun Nov 05, 2017 11:42 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge and stability [ENDORSED]
Replies: 7
Views: 4566

### Re: Formal Charge and stability[ENDORSED]

You want the formal charge on the elements to be as close to zero as possible. Since the formal charge can be negative or positive, the lower the absolute value of the formal charge, the higher the stability.
Thu Oct 19, 2017 1:21 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic Spectra Post Module #42
Replies: 3
Views: 306

### Re: Atomic Spectra Post Module #42

Can someone show their step by step process please? I was using the same method as the one in the second reply but kept getting a really wacky answer.
Thu Oct 19, 2017 1:18 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Wavelength Units
Replies: 5
Views: 418

### Re: Wavelength Units

It can be either, sometimes they just convert it to nm when it converts nicely otherwise they tend to leave it in meters.
Sun Oct 15, 2017 11:57 pm
Forum: Properties of Electrons
Topic: Atomic Spectra [ENDORSED]
Replies: 4
Views: 388

### Re: Atomic Spectra[ENDORSED]

Is n=1 the lowest state for all atoms or just hydrogen atoms?
Sun Oct 15, 2017 11:40 pm
Forum: Properties of Light
Topic: Light travels as a "wave"
Replies: 5
Views: 389

### Re: Light travels as a "wave"

Using the idea of a wave is a easy way to understand of light works. When relating it to ocean waves we can see how it works. Just like the waves can vary in size and how often waves are coming in, the same variations work for light. Different light has different wave lengths and frequencies to use ...
Thu Oct 05, 2017 10:46 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E7 [ENDORSED]
Replies: 9
Views: 769

### Re: E7[ENDORSED]

It's best to round in the final step of the problem to avoid any rounding error.
Thu Oct 05, 2017 9:50 pm
Forum: Balancing Chemical Reactions
Topic: Order of Elements to Balance [ENDORSED]
Replies: 5
Views: 991

### Re: Order of Elements to Balance[ENDORSED]

It is typically easiest to start with the element that occurs the least in the reaction and work your way to the element that occurs the most.